Automatic slack adjuster



FIG. 1 is a left perspective view of an automatic slack adjuster according to our novel design;

FIG. 2 is a front view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof; and,

FIG. 5 is a rear view thereof.

The broken lines in the drawings represent unclaimed environmental subject matter. 

The ornamental design for an automatic slack adjuster, as shown and described. 